Secretogranin II is overexpressed in advanced prostate cancer and promotes the neuroendocrine differentiation of prostate cancer cells.

AIM: In prostate cancer (PCa), neuroendocrine differentiation (NED) is commonly observed in relapsing, hormone therapy-resistant tumours after androgen deprivation. However, the molecular mechanisms involved in the NED of PCa cells remain poorly understood. In this study, we investigated the expression of the neuroendocrine secretory protein secretogranin II (SgII) in PCa, and its potential involvement in the progression of this cancer as a granulogenic factor promoting NED. METHODS: We have examined SgII immunoreactivity in 25 benign prostate hyperplasia and 32 PCa biopsies. In vitro experiments were performed to investigate the involvement of SgII in the neuroendocrine differentiation and the proliferation of PCa cell lines. RESULTS: We showed that immunoreactive SgII intensity correlates with tumour grade in PCa patients. Using the androgen-dependent lymph node cancer prostate cells (LNCaP) cells, we found that NED triggered by androgen deprivation is associated with the induction of SgII expression. In addition, forced expression of SgII in LNCaP cells implemented a regulated secretory pathway by triggering the formation of secretory granule-like structures competent for hormone storage and regulated release. Finally, we found that SgII promotes prostate cancer (CaP) cell proliferation. CONCLUSION: The present data show that SgII is highly expressed in advanced PCa and may contribute to the neuroendocrine differentiation by promoting the formation of secretory granules and the proliferation of PCa cells.

Immunocytochemical distribution of EM66 within the hypothalamic parvocellular paraventricular nucleus: colocalization with CRH and TRH but no plasticity related to acute stress and thyroidectomy in the rat.

EM66 is a secretogranin II-derived peptide strongly expressed within hypothalamic neuroendocrine areas such as the parvocellular aspect of the paraventricular nucleus (pPVN) as well as the median eminence (ME), suggesting a hypophysiotropic role for this neuropeptide. The aim of the present study was to explore such a role in the corticotrope and thyrotrope axes. We analyzed EM66 occurrence respectively in CRH and TRH neurosecretory cells of the rat pPVN by double immunohistochemistry. Functionally, we studied the effect of acute stress (immobilization for 2 h or cold exposure at 5°C for 4 h) and hypothyroidism (induced by 1-week thyroidectomy) on EM66 immunoreactivity (IR) within the pPVN. Double immunohistochemical labeling revealed that EM66-IR colocalized with CRH or TRH labelings within pPVN hypophysiotropic neurons as well as the axon terminals of the external layer of the ME. Because TRH neuronal population of the pPVN is completely distinct from the CRH neurosecretory system, our data demonstrate the existence of at least two distinct EM66 neuronal populations in the rat pPVN. Acute immobilization or cold exposure stresses did not affect EM66 expression as evaluated by the number of EM66-IR neurons within the pPVN. These results suggest that EM66 does not participate to the phenotypic plasticity of hypothalamic parvocellular neurons in response to acute stress. In addition, short-term hypothyroidism did not provoke any significant variation of the number of intraparaventricular EM66 neurons, indicating that EM66 expression would be insensitive to short-term hypothyroidism despite its occurrence within TRH neurons. Thus, the present data show the occurrence of EM66 in distinct areas of the rat PVN but its expression is not coregulated with those of CRH and TRH during acute stress and hypothyroidism.

The neuropeptide 26RFa is expressed in human prostate cancer and stimulates the neuroendocrine differentiation and the migration of androgeno-independent prostate cancer cells.

AIM: Accumulating data suggest that neuropeptides produced by neuroendocrine cells play a crucial role in the progression and aggressiveness of hormone refractory prostate cancer (CaP). In this study, we have investigated the presence and function of the neuropeptide 26RFa in CaP. METHODS: We have localised and quantified tumour cells containing 26RFa and its receptor, GPR103, in CaP sections of various grades. In vitro experiments were performed to investigate the effects of 26RFa on the migration, proliferation and neuroendocrine differentiation of the androgeno-independent (AI) prostate cancer cell line DU145. RESULTS: 26RFa and GPR103 are present in carcinomatous foci exhibiting a neuroendocrine differentiation, and the number of 26RFa and GPR103-immunoreactive cancer cells increases with the grade of CaP. 26RFa stimulated the migration of native or transdifferentiated AI DU145 cells, but had no effect on their proliferation. Furthermore, 26RFa induced the neuroendocrine differentiation of DU145 cells as assessed by the occurrence of neurite-like extensions and the increase of the expression of the neuroendocrine marker chromogranin A. CONCLUSION: The present data indicate that 26RFa may participate to the development of CaP at the AI state by promoting the neuroendocrine differentiation and the migration of cancer cells via autocrine/paracrine mechanisms.

EM66-containing neurones in the hypothalamic parvicellular paraventricular nucleus of the rat: no plasticity related to acute immune stress.

OBJECTIVES AND METHODS: Neuropeptides, as the main neuroendocrine system effectors, regulate notably the response to different stressors via a secretory plasticity within their respective hypothalamic neuronal populations. The aim of the present study was to explore by immunocytochemistry the occurrence and the potential expression plasticity of the novel neuropeptide EM66 in the CRH neurones of stressed rats. RESULTS: The secretogranin II (SgII)-derived peptide EM66 is strongly expressed within hypothalamic neuroendocrine areas such as the parvocellular aspect of the paraventricular nucleus (pPVN) as well as the median eminence, suggesting a probable hypophysiotropic effect of this peptide. As a first approach to investigate such a role, we evaluated by immunohistochemistry EM66 expression within the pPVN following acute immune stress induced by lipopolysaccharide (LPS) or interleukin-1ß (IL-1ß) injection in rat. This study showed that EM66 is present in the pPVN but the number of EM66 immunolabeled cells did not fluctuate in this structure following LPS peripheral injection. In line with this observation, an intracerebroventricular injection of IL-1ß did not provoke any significant variation of the number of intraparaventricular EM66 neurones. CONCLUSION: The present data revealed for the first time that EM66 expression would be insensitive to the central and peripheral cytokines within the neurosecretory hypothalamic pPVN. This result indicates that EM66 does not participate to the phenotypic plasticity of hypothalamic parvicellular neurones in response to acute inflammatory stress.

Granins and their derived peptides in normal and tumoral chromaffin tissue: Implications for the diagnosis and prognosis of pheochromocytoma.

Pheochromocytomas are rare catecholamine-secreting tumors that arise from chromaffin tissue within the adrenal medulla and extra-adrenal sites. Typical clinical manifestations are sustained or paroxysmal hypertension, severe headaches, palpitations and sweating resulting from hormone excess. However, their presentation is highly variable and can mimic many other diseases. The diagnosis of pheochromocytomas depends mainly upon the demonstration of catecholamine excess by 24-h urinary catecholamines and metanephrines or plasma metanephrines. Occurrence of malignant pheochromocytomas can only be asserted by imaging of metastatic lesions, which are associated with a poor survival rate. The characterization of tissue, circulating or genetic markers is therefore crucial for the management of these tumors. Proteins of the granin family and their derived peptides are present in dense-core secretory vesicles and secreted into the bloodstream, making them useful markers for the identification of neuroendocrine cells and neoplasms. In this context, we will focus here on reviewing the distribution and characterization of granins and their processing products in normal and tumoral chromaffin cells, and their clinical usefulness for the diagnosis and prognosis of pheochromocytomas. It appears that, except SgIII, all members of the granin family i.e. CgA, CgB, SgII, SgIV-SgVII and proSAAS, and most of their derived peptides are present in adrenomedullary chromaffin cells and in pheochromocytes. Moreover, besides the routinely used CgA test assays, other assays have been developed to measure concentrations of tissue and/or circulating granins or their derived peptides in order to detect the occurrence of pheochromocytomas. In most cases, elevated levels of these entities were found, in correlation with tumor occurrence, while rarely discriminating between benign and malignant neoplasms. Nevertheless, measurement of the levels of granins and derived peptides improves the diagnostic sensitivity and may therefore provide a complementary tool for the management of pheochromocytomas. However, the existing data need to be substantiated in larger groups of patients, particularly in the case of malignant disease.

The orexigenic activity of the hypothalamic neuropeptide 26RFa is mediated by the neuropeptide Y and proopiomelanocortin neurons of the arcuate nucleus.

26RFa is a hypothalamic RFamide neuropeptide that was identified as the endogenous ligand of the orphan G protein-coupled receptor, GPR103, and that stimulates appetite in mice. Up until now, the mechanism of action of 26RFa in the hypothalamic control of food intake remains unknown. The high density of GPR103 in the arcuate nucleus (Arc) prompted us to investigate, in the present study, the effects of 26RFa on the rat neuropeptide Y (NPY)/proopiomelanocortin (POMC) system. Intracerebroventricular injection of 26RFa stimulated NPY expression and release in the basal hypothalamus, whereas it decreased POMC expression and alpha-MSH release, and these effects were associated with an increase in food intake. A double in situ hybridization procedure indicated that the 26RFa receptor is present in NPY neurons of the Arc, but not in POMC neurons. Central administration of NPY Y1 and Y5 receptor antagonists abolished the inhibitory effects of 26RFa on POMC expression and alpha-MSH release, and reversed 26RFa-induced food consumption. Finally, 26RFa antagonized the effects of leptin on NPY expression and release, POMC expression and alpha-MSH release, and food intake. Altogether, the present data demonstrate for the first time that 26RFa exerts its orexigenic activity by stimulating the release of NPY in the Arc, which in turn inhibits POMC neurons by activating the Y1 and Y5 receptors. It is also suggested that the balance 26RFa/leptin is an important parameter in the maintenance of energy homeostasis.